Inheritance of property

We have a property in Salt Lake, Kolkata of 4.25 Kottas of Land on the basis of an agreement between Govt. of WB and my father. It is a lease-hold property provided for 999 years. My father expired some time back (year 2010) leaving my mother, my elder brother and myself as the legal heir. We appeared before the first class magistrate and in due course of time we 3 were legally identified as the natural heirs to the property. Q1) Can I say that we are now the lease right holders? Moving ahead we applied, along with the affidavit copy, to the local municipal authority with the purpose of having the said property mutated in our name instead of my father’s. The municipal authority has duly acknowledged the same. Based on the above acknowledgement we have also applied for property tax to be now charged in our name. This process as we understand will take some time to be effective. Q2) How long it will take to complete the process? Q3) Will the tax bill issued by the local authority now bears all 3 of our name? In that case in what proportion and how the tax payment is binding on us? Now, moving further ahead, in the above mentioned land, my father during his lifetime had constructed a 3 storied building with the intention of distributing 1 floor each to my mother, my brother and me. Please note that my father had left no will. It is only after his demise that we decided mutually to have the floors distributed in the mentioned order: Top Floor – Elder Brother First Floor – Mother Ground Floor - Me My mother had rented out the first floor and she personally is staying with my brother. Needless to say the income generated from the rent goes to my mother. Just to add, if it is of any relevance to you, she is a pensioner as my father had been a government employee. Q4) In such a scenario can individual floors be in respective occupant’s name in some process which will be legally binding? Q5) If possible can I individually register a floor even when other 2 occupants are not willing to do the same? I understand this mutual understanding has no legal binding and at any point of time can be challenged in the court of law which unnecessarily will lead us to legal harassment which personally I do want to entertain. Q5) If it is not possible to have the floor registered in my name under any circumstances in what way can I safeguard my or future generations claim to the property? Q6) What are the documents do I need to have in my possession?